Electric safety device.



T. l. TOBIN.

ELECTRIC SAFETY DEVICE.

APPLICATION man JULY 3, 191s.

- tain new and Improved Electric Safety De`v UNrrED s'rArEs ra-TENT oEEIcE.

THOMAS J. TOBIN,- OFAL'BANY, NEW YORK, ASSIGNOR TO TE BRYANT ELECTRIC COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPORATION 0F CONNECTICUT.

ELEoTEc SAFETY nEvcE.

Specification of Letters Patent.

Patented Nov. 2, 1915.

Application led July 3, 1913. Serial No. 777,352.

vcitizen of the United States of America, and

residing at Albany, in the county of Albany and State of New York, have invented a cervice, of which the following is a specification.

My invention relates to electric safety devices and receptacles therefor, the object of my invention being to provide an improved t plug and receptacle of the type designed to render it impossible to overfuse a circuit.

In the' accompanying drawing, Figure 1 is a vertical section through a fuse plug and receptacle, detached, in which my invention is illustratively embodied. Fig'. 2 is a similar view showing a plug and receptacle designed for a circuit of smaller capacity;

Figs. 8 and 4 are inverted plan views of the plugs shown in Figs. 1 Iand 2 respectively;

and Fig. 5 is a broken sectionthrough aplug of modified construction.

Various devices have been suggested by which to prevent the yadjustment of a fuse plug of too great capacity in a receptacle arranged in a circuit of relatively low capacity. So far as Iam aware these devices have been of a type which permit the adjustment of the plug in the receptacle, but prevent the engagement of certain of the cooperating contacts unless the plug is of proper capacity. One prominent disadvantage of this type of plug resides in the fact that it is impossible to tell whether or not the circuit has been completed -through the ter in the circuit beyond the plug and this is often not convenient. I am also aware that it has been proposed to provide an elongated center contact rod .below the body of the fuse plug, which enters a well of predetermined diameter below.-tl1e4 ordinary bottom level of the receptacle. Such a c onstruction is extremely inconvenient since it necessitates both fuse plug and receptacle being made almost twice normal length, if the objects which I attain are to be accomplished. The present invention avoids this difficulty by providing a guard which prevents even the partial insertion of the plug, unless the fuse is of proper capacity for the circuit. As here shown, ythe fuse plug comprises the usual insulating body l0 on which is mounted the screw shell 11. Within the plug body isarranged the fuse 12 which is dsoldered at`13 to Ithe center contact. The

latter comprises aperforated guard washer 14 arrangediat the lower extremity of the plug and provided with wings 15 which eX- tend upward therefrom into the interior of the plug. They are preferably of spring metal, in order to insure a close contact with the center contact of the receptacle. The latter comprises the usual shell Contact 16 mounted on the porcelain base 17 and in contact with the wire terminal 18. The center contact comprises a pin 19, preferably threaded at its lower end into the strap 20 which is connected to the other Wire terminal 21. A washer 22 lying beneath a shoul- .der 23 on the pin 19 overlies the centrallyy apertured base of the shell 16 from which it is electrically insulated by the washer 24. The pin 19 is of such diameter with relation to the guard washer 14 that while it passes therethrough, the fit is quite snug.

In Fig. 2 -is shown a plug designed to carry less current. In this case the construction is in all main features the same as in that just described, with the single eX- ception of the diameter of the pin 19L and of the perforation in the guard washer 14a. Both are made largerlthan in the construction shown in Fig. 1. As a result rof this variation in size, which is in each case arbitrarily predetermined with relation to the capacity of the plug, it is obviously impossible to adjust in the receptacle of Fig. 2, the plug of Fig. 1, since the aperture in the guard washer 14 of Fig. 1 is too small to pass over the pin d19a which is of larger diameter. Vhile, on the other hand, the fuse plug of Fig. 2 may be adjusted in the receptacle of Fig. l by reason of the fact that its guard washer 14a has a perforation of a diameter greaterthan that of the pin 19, yet this is attended by no danger, since the fuse in the plug of Fig. 2 is of less cacured within he plug boly 'by the rivet' which is, however, insulated therefrom bythe washer 29.- Thus in this constructionthere can be no possible completion ofthe circuit through the plug untill the pin has entered the interior of the latter. This 1s an added feature of safety which prevents possible misuse of Ythe plug. Various other modiications'of the construction will readily suggest themselves, such for instance as making the pins and apertures in the guard washers` of different shapes for circuits of differentV capacities. I claim as my invention c A 1. A hollow fuse plug having a fuse within the same, a perforated guard at the enteringend of the plug, the diameter of the perforation having a predetermined relation to the capacity of the fuse within the plug, together with 'spring contact means within the plug projecting over the area of thevhole in the guard to engage an entering contact member, for-the purpose described.

2. A plug receptaclev having an insulating base, a screw shell supported thereon, a conducting strap let into the lower face of said base, a center contact pin engaging said strap and projecting into the interior of'said screw shell, said pin having a cross section predetermined with relation to thecapacity of the circuit in which the receptacle is arranged.

vmined with relation to the capacity ofthe -I plug, for the purpose described.

4. Av fuse plug receptacle comprising an insulating v,base having a, screw shell sup-v ,ported thereon and a center contact pin having a diameter predetermined with relation tothe capacity of the receptacle circuit and projecting upward substantially the height of the screw shell, in combinationv with a `fuse plug hollowed to afford a contact chamber anda center contact apertured to permit the entry of said Contact pin 'into the contact. chamber, the diameter of the aperture of said center contact being predetermined with relation to the capacity ofthecircuit which the plug is'designed to protect.

5. A fuse plug receptacle comprising an insulating base `having wire terminals-on its upper face, screw shell and center contact respectively connected 'to said wire terminals, the center contact lcomprising a pin having a diameter predetermined with -relav tion to the capacity lof the receptacle circuit, in combination with a fuse plug havlnga center contact adapted to engage said pin and a' guard disk at the entering end 0f said plug, said guard disk having an aperture the diameter of which is predetermined with re* lation to the capacity of. the plug fuse and through which said center contact -pin passes in the inserted position of the v plug, said v guard pin projecting outward -from the bottom of the receptacle screw shell a distance sufcient to prevent engagement between said screw shell and the coperating member of the plug until the vpin has passed through the guard disk.

In testimony whereof I have signed my name to this speciiicatiomin the presence of two subscribing witnesses.

g 1 THOMAS J. TOBIN;

Witnesses: i I

GEORGE S. GREENE,

JOHN EBEL CAMPION. 

